Answer
$\Delta S_{sys}$ is positive.
$\Delta S_{surr}$ is negative.
The reaction is spontaneous at high temperatures.
Work Step by Step
The number of moles of gas increases from 1 to 2 and therefore entropy of the system increases.
$\Delta S _{sys}$ is positive.
Given that $\Delta H^{\circ}_{rxn}=+393.5 \,kJ$, we have
$\Delta S_{surr}=\frac{-\Delta H_{sys}}{T}\lt0$
If the reaction is spontaneous, $\Delta G\lt0$
$\implies \Delta H_{sys}-T\Delta S_{sys}\lt0$
Since both $\Delta H_{sys}$ and $\Delta S_{sys}$ are positive, $T$ should be high for $\Delta G$ to be negative.
